Receptor interaction has become firmly established as the sole basis for the initiation of target cell response by all endocrine substances. However, as with the molecules themselves, these recognitive entities differ widely in cellular location, molecular properties and functional response. Furthermore, other non-endocrine systems, e.g. the binding and uptake of low density lipoproteins by fibroblasts, appear to share many similarities with various hormore groups. The proposed meeting, scheduled for March 14 - 20, 1982, will examine hormone receptor systems. This symposium will deal with the many receptor types including those at the cell surface, those soluble in the cytoplasm, those associated with intracellular organells, and those in or on the nucleus. Emphasis will be placed on similarities in structure, as revealed by ligand interaction, binding or mono-clonal antibody probes and sequence data, that presumably arise from common origins marking the evolution of this aspect of cell-cell communication. Particular attention will be given to the receptors of closely related substances, such as polypeptide growth factors and adenyl cyclase-dependent hormones. Many of the plenary sessions and workshops will deal with functional responses, e.g. mechanism of action, particularly with respect to the regulation of gene expression. In addition to discussions on the application of the rapidly developing techniques of molecular and cell biology to the further elucidation of receptor structure and function, there is expected to be considerable emphasis on "abnormal" systems (with respect to regulation by external ligands) that characterize encocrine and cancer pathology.